Page 55 - Design Criteria.qxd

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Torque Required To Produce Bolt Stress
The torque or turning effort required to produce a certain stress in bolting is dependent upon a number of conditions, some of which
are:
1. Diameter of bolt
2. Type and number of threads on bolt
3. Material of bolt
4. Condition of nut bearing surfaces
5. Lubrication of bolt threads and nut bearing surfaces
Generally, standard FLEXITALLIC spiral wound gaskets will require that bolting is stressed to 30,000 psi for proper gasket seating.
However, it is a common industry practice to apply a bolt stress equivalent to 50% of yield of commonly used alloy steel bolts, (A 193
B7), to seat standard spiral wound gaskets. The applied force provides for some compensation in bolt up inconsistencies, creep relax-
ation, and other variables associated with flange make up.
Torque Data For Use with Alloy Steel Stud Bolts
Load in Pounds on Stud Bolts When Torque Loads Are Applied
Stress
Nominal Number Diameter Area
Diameter of at Root at Root 30,000 psi 45,000 psi 60,000 psi
of Bolt Threads of Thread of Thread
Torque Load Torque Load Torque Load
(Inches) (Per Inch) (Inches) Sq. Inch Ft/Lbs Lbs Ft/Lbs Lbs Ft/Lbs Lbs
1/4 20 .185 .027 4 810 6 1215 8 1620
5/16 18 .240 .045 8 1350 12 2025 16 2700
3/8 16 .294 .068 12 2040 18 3060 24 4080
7/16 14 .345 .093 20 2790 30 4185 40 5580
1/2 13 .400 .126 30 3780 45 5670 60 7560
9/16 12 .454 .162 45 4860 68 7290 90 9720
5/8 11 .507 .202 60 6060 90 9090 120 12120
3/4 10 .620 .302 100 9060 150 13590 200 18120
7/8 9 .731 .419 160 12570 240 18855 320 25140
1 8 .838 .551 245 16530 368 24795 490 33060
1-1/8 8 .963 .728 355 21840 533 32760 710 43680
1-1/4 8 1.088 .929 500 27870 750 41805 1000 55740
1-3/8 8 1.213 1.155 680 34650 1020 51975 1360 69300
1-1/2 8 1.338 1.405 800 42150 1200 63225 1600 84300
1-5/8 8 1.463 1.680 1100 50400 1650 75600 2200 100800
1-3/4 8 1.588 1.980 1500 59400 2250 89100 3000 118800
1-7/8 8 1.713 2.304 2000 69120 3000 103680 4000 138240
2 8 1.838 2.652 2200 79560 3300 119340 4400 159120
2-1//4 8 2.088 3.423 3180 102690 4770 154035 6360 205380
2-1/2 8 2.338 4.292 4400 128760 6600 193140 8800 257520
2-3/4 8 2.588 5.259 5920 157770 8880 236655 11840 315540
3 8 2.838 6.324 7720 189720 11580 284580 15440 379440
3-1/4 8 3.088 7.490 10000 224700 15000 337050 20000 449400
3-1/2 8 3.338 8.750 12500 262500 18750 393750 25000 525000
3-3/4 8 3.589 10.11 15400 303300 23150 454950 30900 606600
Note: Torque values are based on well lubricated alloy steel bolting.